Scientists have found fossilised remains of what could be the last common ancestor to all the great apes living today. It will give scientists vital clues in charting the course of primate and, ultimately, human evolution.

The fossil, called Pierolapithecus catalaunicus, was found by Dr Salvador Moyą-Solą of the Miguel Crusafort Institute of Palaeontology and colleagues in a village near Barcelona.

The great apes, which include orang-utans, chimpanzees, gorillas and humans, are thought to have developed from the lesser apes, a group that contains modern gibbons and siamangs, about 11m to 16m years ago. The fossil evidence from this period, the middle Miocene epoch, is scanty.

"We don't actually know a lot about the evolution of apes during that time period," said Dr Todd Rae, a palaeoprimatologist at the University of Durham. "In many ways, there's always been a bit of a black hole in terms of good specimens of apes from that particular time period. There's a gap from about 14m to about 7m years ago."

The specimen found by Dr Moyą-Solą was probably male, weighed around 35kg (77lb) and appears to have been a fruit eater because of the shape of its teeth.

Like other great apes, Pierolapithecus had a stiff lower spine, thus affecting its centre of gravity and making it easier to assume an upright posture and to climb trees, the researchers said.

"One of the major changes at the time of this fossil is the change from pronate, the horizontal position of holding your body, to an upright position," said Dr Brooks Hanson, an editor at Science, in which Dr Moyą-Solą's work is published today.

"It's one of the earliest, if not the earliest, showing this change to an upright posture. Obviously you need to go through that transition before you can go through the next transition 7m-8m years later which is to become bipedal."

Scientists said it was likely to be the last common great ape ancestor.

Although Pierolapithecus was found in Spain, Dr Moyą-Solą believes it could have lived in Africa.

"Africa is the factory of primates. In the fossil record of the lower and middle Miocene in Africa, we have found a fantastic diversity of primitive hominoids with monkey-like body structures.

"In Eurasia, apes appeared suddenly in middle Miocene - before then primates there were nearly unknown. For that reason, the source area in my opinion is Africa," he said.

Pierolapithecus is an important tool in helping biologists track exactly how primates adapted to their environment, most crucially in working out the order in which evolution took its course.

"Two things that distinguish human beings from our closest relatives, chimpanzees, are the fact that we stand on our hind legs and we have big brains," said Rae. "But without the relevant fossils, you wouldn't know which came first."

Pierolapithecus will also give scientists clues as to the climate of Europe 13m years ago. "Nowadays we don't have any apes except humans in Europe," said Dr Rae. "Thirteen million years ago, we now know there were apes there. "Most primates are adapted to eat fruit, so that means you'd have to have tropical rainforests. You can think of Europe as being a very different place 13m years ago - it would be equivalent of where we see apes now which are places like the central Africa rainforest or the rainforests of south-east Asia."

Because of the lack of fossils from the middle Miocene, not everyone agrees with Dr Moyą-Solą's placing of Pierolapithecus in the ape family tree.

In an accompanying news article in Science, David Begun of the University of Toronto said certain facial features of the fossil link it to African apes, the group that eventually led to chimpanzees and humans.

David Pilbeam of Harvard University told Science that the new skeleton could be even older than the Spanish scientists had reported. Though the debates will rage for some time to come, no one is in any doubt about the importance of the discovery.

"Evolution is always interpretative because you never have a complete record of things - so you're piecing together what you have," Dr Hanson said. "This is adding a lot of new pieces.

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Perhaps someone would like to take a shot at spinning a new topic out of the content of message 1.